1. Field of the Invention
The present invention relates to a bearing cooling device used for a gear pump for carrying high viscous fluid such as molten resins, and the like.
2. Description of the Related Art
A conventional gear pump for carrying molten resins has a pair of gear rotors. The gear rotor is supported rotatably on a pump body through a bearing. This bearing is a journal bearing, which is a self-lubricating type in which a part of molten resins carried serves as bearing lubricant. In the gear pump of this kind, it is important to increase production amount (carrying amount). Methods for increasing the production amount (carrying amount) include a method for increasing the number of revolutions, and a method for widening face width. However, any of methods increase the burden on the bearing. Therefore, there is high possibility of resulting in backing, and it has not been easy to increase the production amount.
When the number of revolutions is increased, the shearing speed becomes high to increase heat generation of resins. Then, the viscosity of resins lowers, and the bearing support ability lowers. Further, when the face width is widened, the load increases, and the bearing support ability lowers.
In the gear pump of this kind, it is most effective for enhancing the bearing ability to lower the temperature of molten resin as lubricant to raise the viscosity of resins.
Cooling methods for the lubricant (molten resins) include cooling a rotor shaft, cooling a bearing, or a combing the formers.
Incidentally, the cooling of a bearing as described above is important, but there gives rise to a problem that the excessive cooling of a bearing brings forth shrinkage of a bearing itself, as a result of which bearing clearance reduces, resulting in baking.
It is an object of the present invention to provide a cooling device for a bearing for achieving higher speed (higher production amount) of the device and preventing baking of a bearing.
In the present invention, cooling medium is caused to flow into the interior of a journal bearing for supporting a shaft part by lubrication of high viscous fluid and the interior of the shaft part to cool the shaft part and the bearing. The temperature of the cooling medium of the bearing is set to be higher than a temperature of cooling medium of the shaft part.
In this case, preferably, the cooling medium after having been flown into the shaft part is caused to flow into the bearing.
Further, an annular space formed internally of the bearing and a partitioning wall provided spirally within the annular space constitute a cooling medium passage. Preferably, the cooling medium passage is a two-spiral groove.
The bearing cooling device of the present invention is suitably used for a gear pump.